1. Field of Use
This invention relates generally to rack and pinion type jacks for supporting and adjusting the elevation of a trailer tongue. In particular, it relates to a jack wherein movement of the ground-engageable jack support post relative to the jack mechanism housing attached to the trailer tongue can be effected either by rotation of a crank or by a simple sliding motion of the support post itself.
2. Description of the Prior Art
Some prior art rack and pinion type jacks used for supporting and adjusting the elevation of the tongue of a boat trailer or the like comprise a downwardly extending support post, having either a caster wheel or foot plate at the lower end, and having a toothed rack rigidly affixed along one side and a jack mechanism housing attachable to the trailer tongue and through which the post and rack extend. In some such prior art jacks, the mechanism within the housing comprises a crank-driven rotatable pinion gear which is permanently in constant mesh with the rack on the jack post. Rotation of the crank in the appropriate direction effects raising or lowering of the jack post relative to the housing to thereby adjust the elevation of the trailer tongue.
In use, after the trailer tongue is connected to a tow vehicle for road transport purposes but before the trailer is actually towed, it is necessary to raise or retract the jack post upwardly clear of the terrain as far as possible by manually turning the crank in the appropriate direction. Then, after the trailer is towed to its destination but before it is disconnected from the tow vehicle, it is necessary to rotate the crank in the appropriate direction to extend the jack post downwardly so that its lower end contacts the ground for supporting the trailer tongue. Since the distance the post must be raised or lowered may be as much as several feet, and since the distance of post travel linearly per crank revolution is extremely small because of mechanism gear ratios and mechanical advantages involved, the task of cranking is tedious and time-consuming.